Grounding Electrode Conductor (GEC) Calculator
Determine the correct ground wire size for any service or circuit.
What Are You Grounding?
Main Service Panel / Grounding Electrode Conductor (GEC)
Grounding Electrode Conductor (GEC) GECConnects the system grounded conductor to the grounding electrode system.
Main Bonding Jumper (MBJ) / SSBJ Bonding JumperConnects the grounded circuit conductor to the equipment grounding conductor at the service.
Interior Metal Water Piping Bond Water BondRequired bond for metal water piping systems installed in or attached to a building.
Important Notes
•The GEC connects the grounding electrode to the service panel.
•Per NEC 250.66, the GEC is never required to be larger than 3/0 AWG copper.
•The Main Bonding Jumper (MBJ) connects the grounded conductor to the equipment grounding system at the service.
Grounding Sizing Rules
NEC 250.66 & 250.122
Table 250.66 dictates the size of the Grounding Electrode Conductor (wire to ground rod/water pipe). Table 250.122 dictates the Equipment Grounding Conductor (safety ground wire with the circuit).
Frequently Asked Questions
What is the difference between GEC and EGC?
GEC (Grounding Electrode Conductor) connects the system to earth (ground rod). EGC (Equipment Grounding Conductor) connects device metal parts back to the panel to trip the breaker during a fault.
Can I use aluminum for grounding?
Yes, but it cannot be used in direct contact with masonry or earth, and usually must be larger than the equivalent copper wire.
Does the ground wire need to be larger if I increase wire size for voltage drop?
Yes. NEC 250.122(B) states that if ungrounded conductors are increased in size (e.g., for voltage drop), the EGC must be increased proportionately.